1. Field of the Invention
This invention relates to a blast furnace tuyere sensor system in which a photosensitive element detects the light intensities of the several tuyeres and generates an analog voltage signal which can be analyzed to detect deviations from normal tuyere conditions, including a blocked tuyere, nearby "bright" tuyeres or defective sensors, enabling control of coal injection to the tuyeres responsive to such abnormal tuyere conditions.
2. Description of Related Prior Art
With the advent of pulverized coal injection into blast furnaces, it becomes critical to be able to detect problems in the injection system at the tuyeres. As coal injection rates increase, furnace downtime resulting from tuyere, blowpipe, and upper assembly failure also increases, often resulting in catastrophic furnace breakouts and damage to furnace auxiliary equipment.
It is known to use a photosensitive resistor to measure the absence of light from a tuyere through which finely divided coal is being injected into a blast furnace, thereby indicating blockage of the tuyere and enabling coal flow to that tuyere to be shut off. Netherlands patent document 8,901,208 discloses such a system which, for coal flow control, depends on detecting a plugged tuyere from the absence of light as determined by a photoresistor element.
Thus the Netherlands patent allows for the setting of a single "trip point" representing a blocked tuyere enabling the subsequent stopping of coal injection to that particular tuyere. That patent does not permit continuing analysis of the condition of a tuyere or, other than a plugged tuyere, the determination of conditions in nearby tuyeres.
We have found that the condition of tuyeres near to a plugged or blocked tuyere is indicative of possible failure of those nearby tuyeres. Such condition we call a "bright tuyere." We have found that a bright tuyere can be caused by several abnormal conditions, i.e. (1) a plugged injection lance, (2) sensor failure, or (3) coal in the bustle pipe of the furnace feeding air to the tuyeres. The carrying over of coal into the bustle pipe is an emergency condition which must be attended to immediately to avoid catastrophic consequences. When a tuyere shows blocked, while a downstream tuyere shows bright, the bright tuyere condition is being caused by burning coal being carried over from the blocked tuyere. A bright tuyere condition always needs to be investigated to avoid burn out of the tuyere and costly shutdown of the furnace. The Netherlands patent does not permit the determination of a bright tuyere condition or of other conditions, except a blocked tuyere, indicative of system malfunction.